Punz,
Just to get a handle on your idea is this the type of thing you see….

A mainframe program that has two functions.
(1). It takes the TAB prices off the internet and puts them out to a file - we can call the "Prices" file. This file would have the race identifier, TAB number, runner name, win and place prices. The file would be updated regularly as the TAB prices change and can be picked up by a spreadsheet or any other program.

(2) The mainframe also picks up a file that has bets from a spreadsheet - we can call it the "Bet" file. This file has the race identifier, TAB number(s) with betting units and win or place bet. The mainframe job is to pick up the file and format the bets ready for the TAB.

So anyone with a spreadsheet or their own program that has a copy of the mainframe does not have to be concerned about getting TAB prices or setting their bets up for the TAB. All they have to do is pick up the "Prices" file and after they have done all the number crunching and whatever put the bet information into the "Bets" file which will be collected by the mainframe program for action.